This invention relates to electrical connectors of the type having a shell or housing; a plurality of contacts, each of which are connected to separate incoming wires; and a dielectric insert assembly for fixedly or removably mounting the electrical contacts in the connector shell. The invention is more particularly related to the electrical contact assembly and a method of making the electrical contact assembly.
Electrical connectors are utilized in electrical instrumentation to connect together the multiplicity of wires carrying electrical power and signals within and between different electrical instruments making up the system or systems. In the aerospace field, as electronic systems become more and more complex, they are miniaturized to minimize their weight and size. Hence, the electrical connectors interconnecting the systems must also be reduced in size. In some instances, electrical connectors which are no more than a few inches in diameter (called "miniature connectors"), carrying hundreds of electrical contacts which interconnect hundreds of wires. Each of the contacts and wires associated with such a connector are quite small (about one-half an inch lone with a diameter of about 0.092 inches). The wires which are terminated to these contacts generally have a diameter less than about 0.040 inches.
Generally, each of the contacts within the connector is removable so that it may be connected (by crimping) to an incoming wire when the electronic equipment is installed. Each of the incoming wires to the connector is attached to the contact by inserting the electrical wire into an axial opening in one end of the contact and then crimping the contact to the wire to obtain an electrical and mechanical connection. The crimping operation is performed by a well known plier type tool that, when squeezed, applies pressure simultaneously to two pairs of diametrically opposed points in the circumference of the contact to deform the contact wall into the wire within the contact. After the crimping operation, each of the contacts is inserted into the connector insert where they are retained by a contact retention mechanism.
Generally, electrical contacts are machined from metal stock and because of their small size, the contacts are machined to tolerances of 0.002 of an inch or less. A contact which is oversized for any reason cannot be utilized because it may not be possible to insert such a contact into the contact receiving holes in the connector insert or insufficient clearance between contacts could cause an electrical or mechanical problem. One example of an electrical connector having many removable contacts is shown in U.S. Pat. No. 3,721,943 entitled "Electrical Connecting Device" issued Mar. 20, 1973 to Maurice D. Curr.
Machining of electrical contacts is expensive and, because of the large number of contacts utilized by the connector, the connector is expensive. To reduce the cost of manufacturing a connector and at the same time provide an electrical contact that provides a secure electrical and mechanical connection when a wire was crimped to the contact, many inventors have turned to making an electrical contact by stamping and rolling (forming) the electrical contact from a sheet of metal. Examples of such contacts may be found in the following three U.S. patents hereby specifically incorporated by reference: U.S. Pat. No. 3,286,223 "Ferrule Construction and a Method for Producing Same" issued Nov. 15, 1966 to Ronald S. Narozny and Charles C. Anderson; U.S. Pat. No. 3,317,887 entitled "Contact Socket" issued May 2, 1967 to Homer E. Henschen and Marvin L. Yeager; and U.S. Pat. No. 3,721,943 entitled "Electrical Connecting Device" issued Mar. 20, 1973 to Maurice D. Curr.
In each of the foregoing patents, the inventors found it necessary to weld or braze the joint or seam that resulted when the contact was formed by rolling the flat stock. In the Curr patent, the abutting edges of the seam were brazed together. In the Narozny patent the edges that formed the seam were overlapped and spot welded together. As pointed out in the Curr patent, the seam is brazed so that the end portion of the contact is continuous around its circumference without any break therein. This approach enabled the end of the contact to be crimped to the end of a wire irrespective of the rotational position of the contact relative to the crimping tool. In most connectors used by the military and the aircraft industry, the wire is crimped to the contact at four points (about 90.degree. apart). As pointed out in the Curr patent, when the free ends are not attached (not welded or brazed) to each other, the action of the edges of the open seam in the contact become displaced with respect to each other during the crimping operation so that a secure electrical and mechanical connection to the wire and contact does not occur. In addition to this, the crimping operation on a contact having an unbrazed or unwelded (open) seam can cause the end portion of the contact to distort unsymmetrically so that it becomes oversized and cannot be properly inserted into its position in the electrical connector.
Therefore, there have been many attempts to replace machined contacts with less expensive electrical contacts stamped and formed from a sheet of metal. In addition to this, inventors have been searching for practical alternatives to brazing or welding the seam that occurs in a contact formed from a stamping. The difficulty of welding or brazing the seam is emphasized when one considers that the sheet metal from which the contact is formed is only about 0.005 inches thick and the longitudinal seam is only a very small part of the contact diameter of about 0.048 inches (about the diameter of paper clip wire).